Paste properties

Denaturation and aggregation of whey proteins are affected by the pH of extrusion. When extruding WPI, alkaline conditions increase denaturation and solubility, decrease pasting properties, and produce more pronounced microstructural changes (Onwulata et ah, 2006). Denaturation in the extruder causes whey proteins to form small primary aggregates that combine to form large clusters. The clusters are then aligned by shear to form fibrous structures. 

Based on these results, several different commercial and experimental protease samples were obtained from enzyme companies and were tested for starch yield using the enzymatic corn wet milling process (Figure 3). Two commercial protease enzymes (enzymes A and C) gave starch yields comparable to the conventionally wet milled sample. Pasting properties, residual protein in starch, and surface characteristics of starch samples obtained from... 

Singh, V., Haken, A.E., Dowd, M.K., Niu, Y.X., Zou, S.H., and Eckhoff, S.R. 1999a. Batch steeping of com Effects of adding lactic acid and sulfur dioxide at different times on starch yields, protein contents, and starch pasting properties. Cereal Chem. 76, 600-605. 

Singh, V. and Johnston, D.B. 2002. Pasting properties and surface characteristics of starch obtained from an enzymatic com wet-milling process. Cereal Chem. 79, 523-527. 

Grain legumes have also been processed into refined starch (10,11) and protein isolates (12,13,14) by procedures derived from the traditional corn starch and soybean protein industries (15). However, comparative data on product yields, composition and losses have not been published. A commercial plant for the wet processing of field pea into refined starch, protein isolate and refined fiber has been established in Western Canada. Little is known about the characteristics of the protein isolate or refined fiber product. Water-washed starch prepared from the air-classified starch fractions of field pea (16,17) and fababean (6) have been investigated for certain physico-chemical and pasting properties. Reichert (18) isolated the cell wall material from soaked field pea cotyledons and determined its fiber composition and water absorption capacity. In addition, the effects of drying techniques on the characteristics of pea protein Isolates have been determined (14). 

Jane, J., Chen, Y. Y., Lee, L. F., McPherson, A. E., Wong, K. S., Radosavljevic, M., and Kasemsuwan, T. (1999). Effects of amylopectin branch chain length and amylose content on gelatinization and pasting properties of starch. Cereal Chem. 76, 629-637. 

Gelatinization of sweet potato, tania, and yam tuber starches. Starch/Starke. 47, 298-306. Varavinit, S., Shobsngob, S., Varanyanond, W., Chinachoti, P., and Naivikul, O. (2003). Effect of amylose content on gelatinization, retrogradation and pasting properties of flours from different cultivars of Thai rice. Starch/Starke 55,410-415. 

Viks0-Nielsen, A., Blennow, A., Kristensen, K. H., Jensen, A., Moller, B. L. (2001). Structural, physicochemical, and pasting properties of starches from potato plants with repressed ri-gene. Biomacromolecules, 3, 836-841. 

Suzuki, A., Shibanuma, K., Takeda, Y, Abe, J. and Hizukuri, S. (1994). Structures and pasting properties of potato starches from Jaga Kids Purple 90 and Red 90. Oyo Toshitsu Kagaku, 41,425-432. 

Kaur, L., Singh, J., Singh, N., Ezekiel, R. (2007). Textural and pasting properties of potatoes (Solanum tuberosum L.) as affected by storage temperature. J. Sci. FoodAgric., 87, 520-526. 

Lim, S. T, Lee, J. H., Shin, D. H., Lim, H. S. (1999). Comparison of protein extraction solutions for rice starch isolation and effects of residual protein content on starch pasting properties. Starch, 51, 120-125. 

Wu, Y, Seib, P. A. (1990). Acetylated and hydroxypropylated distarch phosphates from waxy barley paste properties and freeze-thaw stability. Cereal Chem., 67, 202-208. 

Almost all the starches investigated contain some phosphorus.124-126 In addition to phospholipids, phosphorus is also commonly found in starch as monostarch phosphate esters.6,7 Inorganic phosphate is present in some starches.124-126 Monostarch phosphate esters and phospholipids have different effects on starch paste properties.133,135 Monostarch phosphate esters, found in potato, shoti and other starches,6,7,136-140 increase paste clarity and paste viscosity.79 Little phosphate monoester is found in cereal starch.121,124,141,142 Phospholipids, found in normal cereal starches (e.g. wheat, rice and maize) decrease paste clarity and viscosity.133 31P-nmr spectroscopy has... 

Paste properties of native starches from different botanical origins have been reviewed.92,133 Relevant to practical usage of starch, the most important paste properties are viscosity, texture, paste transparency, resistance to shear and tendency to retrograde. In terms of texture, the translucent potato starch pastes can be described as cohesive, long-bodied, stringy and rubbery. Other root, tuber and waxy starches give pastes of similar texture to that of potato starch, but are generally less cohesive. On the other hand, pastes from common cereal starches are opaque and can be described as noncohesive and short- and heavy-bodied. These and other properties of several native starches are summarized in Table 8.1. 

Table 8.1 Gelatinization and pasting properties of native starches130...

Table 10.13 Effect of degree of crosslinking on pasting properties of large granule wheat starch at 10% solids27...

Table 12.7 Gelatinization, pasting and paste properties of starches from different botanical origins3...

The Rapid ViscoAmylograph (RVA) has been the preferred instrument for determining the pasting properties of rice flour and rice starches24,25 (see Chapter 8). 

Heat treatments at various moisture levels have been shown to affect starch properties, including paste stability to heat, shear and storage. These treatments can be classified as annealing with moist heat and dry heat, and are best characterized by their impact on moisture absorption, differential scanning calorimetry (DSC), x-ray diffraction patterns and pasting properties. There is some similarity in the affects of the three on starch properties only relatively recently have the differences been recognized. 

Generally, the phosphorus content in starches is associated with different pasting properties, and it confers a larger ion binding capacity. In wheat and com starch, phosphorus is present largely or wholly as adsorbed phos-phatides (extractable with boiling 85% methanol) associated preferentially with the amylose fraction. 

The pasting properties of quinoa starch are reported by Qian and Kuhn (1999) and show a pasting temperature of 66.8 °C, comparable to quinoa starch pasting values (63-64 °C) reported by Lindeboom (2005). 

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